In recent years, the OFDM scheme, which enables high speed and large capacity and which improves error robustness, has been studied toward next-generation mobile communication systems. The art disclosed in Patent Document 1 is an example of the OFDM scheme. This art will be briefly described below.
As shown in FIG. 1, the transmission system disclosed in Patent Document 1 generates signals in which a predetermined part of the rear part of transmission data (data part in the drawing) is attached to the beginning of the data part as a guard interval (hereinafter abbreviated as “GI”.) The signals generated as such are transmitted from the transmitting apparatus, and signal combined a direct wave with a delayed wave in a channel are received in a receiving apparatus.
At receiving apparatus as shown in FIG. 2, a timing synchronization process is performed for the received data, and signals of the length of the data part are extracted from the beginning of the data part of the direct wave. The extracted signals thereby include the direct wave component, the delayed wave component and the noise component from receiving apparatus. And the extracted signals combine all of these components. Then, FFT (Fast Fourier Transform) is performed to the extracted signal and the result is demodulated.    Patent Document 1: Japanese Patent Application Laid-Open No. 2004-40507